Operate LEDs for long time with batteries

I want to operate 30 smd LED at the same time but with batteries. I chosen a 18650 Li-ion battery because of it's capacity but I was so disappointed when after my calculating, I got the result that this battery can only operate for only 5 hours before gets emptied.
Is there ANY way to make it last for months? (not with ridiculous amount of batteries)


Reduce the current used by the LEDs ?

Actually, it will be hooked up to an LDR sensor, when it's daytime the LEDs will be on max load, when it us nighttime, the LEDs will be on minimum load. So I can't really play with that option

Why do you need to run LED's on batteries for months?

Have you considered adding solar to your project which would allow the batteries to be recharged and with reduced current and another battery or 2.

Oh, you are running a LDR and what else on batteries?

I'm not sure if the solar recharge enough

Basically this is the whole thing, LEDs operated from battery with an LDR sensor for brightness adjusting

I run this weather station on solar.

2 CPU's and a dozen sensors. 24/7, sending data 11 times a second. Solar recharges that battery.

Well, I don't have that much space, it is just around 400x30x150 mm procjet thats why I wanted to use a 18650 battery

Solar would be a solution, too bad you can't do solar. Luck to you in coming up with a solution.

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Sounds like you need a perpetual energy battery.

Or a long power supply wire.

Thank, I'm afraid there is no solution :confused:

A what? :smiley: I don't want it to be wired cause it will be on the wall

Like I said a perpetual energy battery.

One day they might be invented.

Wait, and how 7 segment displays work then? Are they not individual LEDs?

You might be able to double the battery life by reducing the LED current, both day and night. 25mA is probably the maximum current for the LED, but you may not actually need anywhere near that much, particularly if there are 30 of them. And of course you could put two to four 18650's in parallel.

But I don't think running 30 LEDs for months on one 18650 is in the cards unless you use solar power to both power the LEDs and recharge the battery during the day, and then run the LEDs at very low current at night.

Are you using white LEDs? Vf for red might be around 1.8V at 10mA or lower, which might let you use two in series. That's right on the edge though, and might not work.

So I think you need to go back and re-examine what you really need - how many LEDs, how much current. Do they need to be on continuously, or could they be blinking, or perhaps fire sequentially? You might want to describe what you're doing in a bit more detail. Maybe someone here will have an idea.

Yes, I want to use white LEDs just because of the color (I know it has the highest consuption). I could use 2 batteries but I don't think it would be enough, even if I reduce to 10mA/LED it will only last for about 13 hours with one battery. As I described, I want to use the LEDs in different combinations (the "worst" scenario for the power when all 30 LED are turned on) and when it's daytime the LEDs will be on max (or bigger) load for brightness, when it us nighttime, the LEDs will be on minimum load. I don't want it to be wired, and don't have too much space.

Use a much larger capacity battery.

Example: 10 mA x 30 LEDs x (24*30) hours/month =216 Ampere hours, for one month of continuous illumination.

Your call.

I'm going to take a wild guess here that you're building a clock of some sort, since you mentioned 30 LEDs and 7-segment displays (4 digits plus a colon comes out to 30 LEDs).

If that's the case, then the LEDs are used for indication rather than for illumination, so you can probably get away with running them with very little current. Run some experiments to see how low you can go while still being visible in whatever conditions it'll be used in. You might be able to drop them to 0.25 mA or lower, which would increase the run time to 20 days (and maybe a month or more since the current draw will be even lower at night). And assuming this is a clock, not all segments will be lit simultaneously; in fact, only about 2/3 will be lit at the same time, on average. So the average current consumption will be slightly lower than with all 30 LEDs lit all the time.

If 0.25 mA isn't enough to make the LEDs bright enough, perhaps you could add a dimming/undimming feature (e.g., push a button to show the time, then dim again after a few seconds).

Hi, @delta_fox,
when you get a battery as big or smaller as an 18650 that can deliver 200 Ah, let me know, and we'll sell it at Tesla.
let's become millionaires.

RV mineirin

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